This invention relates generally to lighting fixtures and, more particularly, to lighting fixtures configured to image a high-intensity beam of light at a distant location.
Lighting fixtures of this particular kind are commonly used in theater, television and architectural lighting applications. Such fixtures typically include an ellipsoidal or near-ellipsoidal reflector with a single lamp located generally coincident with the reflector's longitudinal axis. The reflector defines two focal regions, and the lamp is positioned generally with its filaments located at or near a first of those two focal regions, such that light emitted from the filaments is reflected by the reflector generally toward the second focal region. A gate is located at that second focal region, and shutters, patterns and the like can be used at the gate for shaping the projected beam of light. A lens located beyond the gate aperture images light passing through the aperture at a distant location. An example of a lighting fixture of this particular kind is set forth in U.S. Pat. No. 5,345,371, issued Sep. 6, 1994 and entitled "Lighting Fixture."
Lighting fixtures of the kind described above typically include projecting lenses formed of glass, with spherical and/or aspherical surfaces. Aspheric glass lens are considered expensive, especially in the case of fixtures that provide narrow beam widths, which require the lenses to have diameters as large as 12 inches. Use of the spherical lens, of course, leads to certain aberrations that detract from the quality of the projected image.
Another drawback to the use of glass lens in such fixtures is that the glass is considered to introduce excessive weight to the fixture. In the case of fixtures that project beams of narrow beam width, this excessive weight can introduce an imbalance in the fixture, which can cause slippage or can require a complicated support mechanism.
It should therefore be appreciated that there is a continuing need for a lighting fixture of this kind that is configured to image a high-intensity beam of light at a distant location with reduced manufacturing expense and with reduced weight. The present invention fulfills this need.